This invention relates to intermittent feed mechanisms and, more particularly, to an intermittent feed mechanism which is to be efficiently assembled with deviation in pawl tip position suppressed.
FIG. 9 is a schematic top view showing a conventional intermittent feed mechanism. In this intermittent feed mechanism 500, reference numeral 501 designates a counting wheel. This counting wheel 501 has a counting second hand shaft 511 attached with a minute feed pawl 512 acting parallel to the plane of the counting wheel 501. The minute feed pawl 512 has an elongate spring portion 514 extending from a body portion 513 and a pawl portion 515 formed at a tip of the spring portion.
This pawl portion 515, each time rotating by one turn, engages a gear tooth of the minute counting intermediate wheel 502. In order to properly engage the gear, highly accurate tip position is required for the pawl portion 515. The tip position is adjusted by bending the spring portion 514 during assembling. Meanwhile, a heart cam 516 is mounted on the counting second hand shaft 511. Reference numeral 517 is an eccentric pin that penetrates through the heart cam 516 and counting gear 518. Also, the minute feed pawl 512 is positioned by inserting the eccentric pin 517 in an opening 519 thereof.
Next, the operation of the intermittent feed mechanism 500 will be explained. The rotation of a barrel complete is conveyed to the counting wheel 501 through a counting intermediate train wheel. The counting wheel 501 rotates one turn in 60 seconds. Each time the counting wheel rotates by one turn, the pawl 515 of the minute feed pawl 512 engages the gear of the minute counting intermediate wheel 502. The minute counting intermediate wheel 502 is intermittently moved at one tooth of its gear, pushed by the pawl 515 in rotation. Actually, the rotation of the minute counting intermediate wheel 502 is decelerated and conveyed to the minute counting wheel (not shown).
Meanwhile, the heart cam 516 is rotated by the rotation of the counting wheel 501. Upon zero returning, a hammer at a tip of a hand returning lever is pressed on the heart cam 516 to thereby forcibly rotate the heart cam 516. Although there is a possibility that the pawl portion 515 contacts the gear of the minute counting intermediate wheel 502 due to rotation of the heart cam 516, the counting wheel 501 rotates without causing problem because the elasticity of the spring portion 514 releases the pawl portion 515.
However, in the conventional intermittent feed mechanism 500, the minute feed pawl 512 is fabricated by press-blanking and thereafter subjected to heat treatment. Thus, there has been a problem that the pawl portion 515 deviates from the ideal tip position. The positional deviation in the pawl portion 515 tip possibly causes such trouble as insufficient or excessive force fed to the counting intermediate wheel. For such problems, in conventional devices the spring portion 514 is bent and adjusted during assembling. However, there has been a problem with the time taken for adjustment due to problems such as springback of the spring portion 514, resulting in worsened assembling efficiency. Furthermore, there is another problem that the assembling process steps are increased in number due to fine tip position adjustment of the pawl portion 515 using the eccentric pin 517.
Therefore, this invention has been made in view of the above, and it is an object to provide an intermittent feed mechanism which is to be assembled with efficiency with deviation in pawl tip position suppressed.
In order to solve the above problem, an intermittent feed mechanism according to the invention has a positioning portion for positioning a feed pawl provided on a counting wheel and provided in part of a structural member of the counting wheel.
If instead of adjustment by bending the spring portion, in this manner a positioning portion for positioning a feed pawl is provided separately, the adjustment by bending or fine adjustment with an eccentric pin is not required. Also, the position deviation of the tip of the feed pawl is reduced.
In another embodiment, an intermittent feed mechanism has a feed pawl having a spring portion provided on a first counting wheel. The feed pawl rotates together with the first counting wheel so that with every turn the feed pawl engages a gear of a second counting wheel or a second counting intermediate wheel, thereby intermittently feeding force to the second counting wheel or the second counting intermediate wheel. A positioning portion is provided in part of the feed pawl, and the feed pawl is positioned by urging the positioning portion on a predetermined portion of the first counting wheel by a spring portion of the feed pawl.
That is, the positioning portion provided on the feed pawl is urged on a predetermined portion of the first counting wheel by the spring portion possessed by the feed pawl. This can generally determine, in the predetermined portion, the tip position of the feed pawl. Accordingly, the feed pawl rarely deviates in its feed pawl tip position. Also, the predetermined portion, if previously machined with accuracy, makes unnecessary any adjustment through bending or the like. Fine adjustment with the eccentric pin is also unnecessary.
In another embodiment, an intermittent feed mechanism has a feed pawl having a spring portion provided on a first counting wheel. The feed pawl rotates together with the first counting wheel so that at every turn the feed pawl engages a gear tooth of a second counting wheel or a second counting intermediate wheel thereby intermittently feeding the second counting wheel or the second counting intermediate wheel. A protrusion is provided on the feed pawl, a positioning hole is provided in a structural member of the first counting wheel, the protrusion being inserted in the positioning hole, and the protrusion being urged in the positioning hole by a spring portion of the feed pawl thereby positioning the feed pawl.
A protrusion is provided on the feed pawl and a positioning hole is provided in the first counting wheel. During assembling the protrusion is inserted in the positioning hole and the protrusion is urged in the positioning hole by the spring portion possessed by the feed pawl. This can generally determine, in the predetermined portion, a tip position of the feed pawl. Accordingly, the feed pawl rarely deviates in feed pawl tip position. Also, the above positioning hole, if previously machined with accuracy, makes unnecessary any adjustment through bending or the like. Furthermore, the eccentric pin can be omitted.
Next, an intermittent feed mechanism according to another embodiment of this invention is characterized in that in the intermittent feed mechanism a protrusion at the tip is made in a hook form.
If in this manner the protrusion is formed in a hook form at the tip, when inserted in the positioning hole the protrusion and the positioning hole hardly disengage only with difficulty.
In another embodiment, an intermittent feed mechanism has a feed pawl having a spring portion provided on a first counting wheel. The feed pawl rotates together with the first counting wheel so that with every turn the feed pawl engages a gear tooth of a second counting wheel or a second counting intermediate wheel, thereby intermittently feeding force to the second counting wheel or the second counting intermediate wheel. A protrusion is provided on a structural member of the first counting wheel, a portion other than the portion to engage the gear of the feed pawl being urged on the protrusion by the spring portion, thereby positioning the feed pawl.
In this case, a protrusion is provided on the side of the counting wheel with the structural member so that the feed pawl is urged on the protrusion. This also can generally determine through the protrusion the feed pawl tip position. Accordingly, the feed pawl hardly deviates in its tip position. Also, adjustment by bending or the like is unnecessary and the eccentric pin can be omitted.